Thermodynamic simulation of alternative absorption heat pumping processes using natural working fluids

Three groups of alternative absorption heat pumping processes (AHP) with different natural working fluids are being analyzed in this paper: Absorption heat transformer (AHT) process using partially miscible working mixtures; AHP-processes using a condensable auxiliary fluid (Einstein–Szilard cycle, Rojey cycle); NH3/H2O-AHP-process using strong bases as additives (e.g. NaOH).The thermodynamic simulations have shown that a NH3/H2O absorption cycle using a strong base as additive seems to be promising for applications using low-grade heat sources and the Rojey cycle offers higher COPs than a conventional NH3/H2O-AHP at high generator temperatures and low temperature lifts. The investigated AHT-process and the Einstein–Szilard process seem presently not to be competitive compared to conventional technologies.At present the influence of strong bases on a conventional NH3/H2O-AHP is being investigated at the Institute of Thermal Engineering, Graz University of Technology.

► We analyze different alternative absorption heat pumping processes. ► The NH3/H2O/NaOH AHP-process is promising at low generator temperatures. ► The Rojey cycle is promising at low temperature lifts. ► Tests on the NH3/H2O/NaOH AHP test rig are being carried out.